Soap stabilizer



Patented Fol 4, 1 936 UNITED STATES SOAP STABILIZER Robert M. Reed, Cincinnati, Ohio, assignor to The Procter 8r Gamble'Company, Cincinnati, Ohio,

a corporation of Ohio No Drawing.

' 6 Claims This invention relates to the stabilization of soap or soap products, with particular reference to the prevention or retarding of the discoloration, or rancidiflcation of, same.

The object of the invention is to improve the quality of soap products, especially the keeping quality of same as evidenced by the tendency to discolor or develop rancidity.

Many soap products will discolor and develop changes depend somewhat on storage conditions, but commonly occur in soaps made from lower grades of fats, or if the soaps are contaminated with very small amounts of metals. Extremely minute amounts of certain metals, orsalts of metals, especially copper, (even when present in such minute amounts as one part per million) .act as catalyzers and strongly accelerate the development of discoloration and rancidity in soaps when otherwise the soap in question might retain its original good color and sweet odor practically unchanged for many months or even years. Such small contaminations often occur from accidental causes. 25 I have found that the incorporation of very small amounts (0.01% to 1%) of some one of the para-tertiary phenols, such as the para-tertiary'butyl phenol and para tertiary amyl phenol, in soap will prevent or greatly retard the development of discoloration and rancidity, whether due to the presence of metals or their salts, or to other causes.

I am aware that certain phenols have been proposed for use in various organic materialsas preservatives or stabilizers against-changes due both to bacterial action and to oxidation. How- .ever, there has been no general principle by which it could be, predicted whether a given phenolic body or class of phenols would preserve or harm the color and odor of soap on aging. For instance, phenol itself and the cresols, when used in small quantities, have only a slight preservation action on soap; thymol has a marked stabilizing action; resorcinol, pyrogallol, and vanillin, on the contrary, all cause marked discoloration in soap on aging. All these substances belong in the group of phenols, although in diiferent sub-groups.

I have discovered that para-tertiary-butyl phenol and para-tertlary-amyl phenol are highly eiiicient preservatives when used in small quantitles in soap, from which it appears evident that other para-tertiary phenols will act in the same way. In the range of ordinary conditions I find Ii that an amount of either phenol equal to about on objectionable rancid odor on aging. These Application August 29, 1933, Serial No.68'L336 0.01% to 0.25% of the weight of the soap gives good results. Even lower amounts of these phenols are of value as soap preservatives, especially if used in conjunction with other known preservative materials, such as certain perfume bodies. 5 A proportion of these phenols greater than about- 1% may be objectionable by introducing a characteristic discoloration and odor of their own, even though the ordinary discoloration and rancidity of the soap itself are prevented.

In carrying out my invention, the para-tertiary phenol stabilizer may be added to thesoap in any convenient manner during the usual crutching or milling or other similar operation, care being taken to secure. a uniform distribution throughout the entire mass of soap. My preferred way is to'dissolve the stabilizer in the perfume which is to be added to the soap and then add the mixture. The stabilizer may, however. be dissolved in some other suitable solvent, or it go may be added in a finely ground condition directly to the soap without first being dissolved, if desired. In case of milled soap, I prefer to addthe stabilizer during the milling operation, but in case of other soaps the most convenient place for addingit is in the crutcher. An amount of these stabilizers equal to -02% to .05% usually gives good results on ordinary grades of toilet soaps, but smaller quantities or considerably larger quantities may be used if desired. The amyl compound appears to be slightly more eifective than the butyl compound when equal percentages are compared.

The following experiments will illustrate the value of these two phenols as preservatives in soap. Samples of soap were prepared and subjected to an accelerated aging test which consists in subjecting the samples to a temperature of 140 F. Under this accelerated aging condition the discoloration at the end of nine days is approximately the same as would be shown after one year under ordinary conditions.

Samples were as follows: Y

No. 1. White milled soap, containing no added preservative and no added copper.

No. 2. White milled soap containing no added preservative, but containing p. p. m. of copper. added in the form of copper sulphate.

No. 3. White milled soap, containing 0.02% para-terti'ary-amyl phenol and 20 p. p. m. of added copper.

No. v4. White milled soap, containing 0.2% of para-tertiary-amyl phenol and 20 p. p. m. of added copper.

' No. 5. White milled soap, containing 0.02% of.

para-tertiary-butyl phenol and 20 p. p. m. of added copper.

No. 6. White milled soap, containing 0.2% of para-tertiary-butyl phenol and 20 p. p. m. of added copper.

The purpose of the copper was to ensure a discoloration of the soap on aging in order to show the improvement resulting from adding the preservative. The preservatives and the copper were added to the soap during the milling operation and uniformly distributed in the soap; they were dissolved in alcohol before being added.

The samples were examined after exposure to the temperature for respectively nine days, seventeen days, twenty-four days and thirtyone days. The soap containing no added preservative or copper held its color almost un-.

changed throughout the entire period, due to the good quality of soap and freedom from impurities. but no preservative, showed marked discoloration after nine days, and progressively darker discoloration at each successive examination until after thirty-one days it was extremely dark. Sample No. 3, containing 0.02% of the amyl compound and 20 p. p. m. of added copper, showed no discoloration until after twenty-four days, at which time it was extremely slight, and after thirty-one days it was slightly dark, but not nearly as dark as sample No. 2 after only nine days. This indicates that a soap containing 0.02% of paratertiary-amyl phenol will discolor less in three and a half years under normal conditions than will the same soap without phenol in one year. Sample No. 4, containing 0.2% of para-tertiaryamyl phenol and 20 p. p. m. of added copper, retained its original color practically unchanged even after thirty-one days in the accelerated test. This indicates that a soap containing 0.2% of para-tertiary-amyl phenol will resist discoloration for a period considerably greater than three the phenol for one year.

Sample No. 2, containing the copper I and a half years, than will the same soap without Samples 5 and 6, containing the butyl phenol in place of the amyl phenol showed similar results to samples 3 and 4,

respectively, except that they were not quite as efilcient in their preservative action as the corresponding amyl phenol;

These' experiments carried out under accelerated aging conditions, have been confirmed by similar tests under normal aging conditions carried out over a considerable period of time.

So far as I am advised the other para-tertiary phenols will possess like properties to the amyl and butyl phenols to which I have directed my principal attention and I consider them as the equivalents oi the amyl and butyl phenols.

Having thus described my invention, what I claim as new and desire to secure in Letters Patent, is:-'

1. The process of stabilizing soap products which comprises incorporating therewith paratertiary-amyl phenol.

2. A stabilized soap product comprising soap and para-tertiary-amyl phenol.

3. The process of stabilizing soap products which comprises incorporating therewith an amount of para-tertiary-amyl phenol not exceeding 1% of the weight of soap.

4. A stabilized soap product comprising soap and an amount of para-tertiary-amyl phenol not exceeding 1% of the weight of soap.

5. The process of stabilizing soap products which comprises incorporating therewith a quantity of para-tertiary-amyl phenol amounting to between 0.01% and 0.25% of the weight of soap.

6. A stabilized soap product comprising soap and a quantity of para-tertiary-amyl phenol amounting to,between 0.01% and 0.25% of the weight of soap.

1 ROBERT M. REED. 

